This invention relates to devices for removing dents and more particularly to devices for removing dents from electrically conductive materials using electromagnetic energy.
In the past, devices adapted to remove dents from conductive materials using electromagnetic energy have been proposed and used. One such device is described in U.S. Pat. No. 3,998,081 referenced above. With respect to U.S. Pat. No. 3,998,081, the information contained therein, particularly the information describing the production and application of electrical current to the electromagnetic working coil of an dent removal head, is incorporated herein by reference.
While electromagnetic dent removers of the type described in U.S. Pat. No. 3,998,081 have proven to be somewhat satisfactory, they are not as satisfactory as desirable. One area remaining subject to improvement is the electromagnetic work coil forming part of the dent removal head. More specifically, as it will be recognized by those skilled in the art and others, the configuration of the electromagnetic working coil is important to the successful operation of an electromagnetic dent remover. Generally the configuration of such coils has heretofore been subject to conflicting design constraints leaving the designer no choice but to compromise various design objectives. From a magnetic parameter standpoint, the design objective is to effectively achieve a localized area of flux concentration (stressing region) by employing a high magnetic field to current ratio. From a geometrical standpoint, the design objective is to have a size and shape the conforms to the geometry of small dents so that the forces do not act on the metal surface beyond the boundaries of the dent, while providing a coil large enough to ensure that the magnetic field does not decrease too rapidly with respect to the thickness of the dented metal. From a mechanical standpoint, the dent removal coil must be rugged enough to withstand the deformation and deflection forces created by the second current pulse. Further, the coil must be economically producable. Also, thermal characteristics must also be considered, since a considerable amount of thermal energy is produced, especially during the slower rising first current pulse. Finally, the coil's electrical characteristics must be compatible with the current source circuitry. Further, since a large variety of dent configurations may be encountered, it is advantageous to construct the dent remover such that dent removal heads having variously configured electromagnetic working coils can be utilized.
In U.S. Pat. No. 3,998,081 several working coils are disclosed, along with a method of manufacturing them. Generally each coil is formed by spirally winding a conductive wire rod or ribbon coated with a non-conductive material. In each of the configurations, the magnetic flux is concentrated in a stressing region by forming the coil such that only a desired portion thereof is in close proximity to the dent when the dent removal head is suitably positioned. The coil is formed to a desired shape by electromagnetically deforming a flat spiral wound coil placed within a mold structure. Since the strength of the electromagnetic field coupled to the dented material varies as a function of the distance between the windings of the coil and the work surface, the nature of the coil deformation controls the flux concentration area. Hence, appropriately deforming the coil will result in the production of a flux pattern suitable for use with dents falling within a predetermined size range.
Although coils formed in accordance with the teachings of application Ser. No. 489,290, referenced above, perform satisfactorily and are amenable to economic fabrication, they are not as satisfactory as desirable in certain other aspects. The present invention is directed to overcoming these disadvantages.
Accordingly, it is an object of this invention to provide dent removal heads having new and improved electromagnetic work coils.
It is a further object of this invention to provide new and improved electromagnetic work coils that are inexpensive to manufacture yet are readily formed so as to be useful in removing dents from objects having a wide variety of sizes and shapes.
It is another object of this invention to provide economically producable electromagnetic work coils having improved mechanical strength, good thermal characteristics and relatively small size, yet capable of producing an adequately strong locally concentrated electromagnetic field.
It is yet another object of this invention to provide electromagnetic dent removal apparatus including new and improved electromagnetic work coils suitable for use in removing dents from a wide variety of conductive materials shaped and sized in various manners.